Advice on external hard drives?

Hey everyone Apologies because this is probably a rookie question

I have a 500gb ps4 and lo and behold I filled it up pretty quick

I've been reading online that if you own an external hard drive you can format it and then begin saving everything on that instead of the ps4 memory.

Can anyone recommend a reliable external hard drive that isn't too expensive?

Thanks and sorry again if this is a retread